Distributed systems allow multiple clients in a network to access a pool of shared resources. For example, a distributed storage system allows a cluster of host computers to aggregate local disks (e.g., SSD, PCI-based flash storage, SATA, or SAS magnetic disks) located in or attached to each host computer to create a single and shared pool of storage. This pool of storage (sometimes referred to herein as a “datastore” or “store”) is accessible by all host computers in the cluster and may be presented as a single namespace of storage entities (such as a hierarchical file system namespace in the case of files, a flat namespace of unique identifiers in the case of objects, etc.). Storage clients in turn, such as virtual machines spawned on the host computers may use the datastore, for example, to store virtual disks that are accessed by the virtual machines during their operation. Because the shared local disks that make up the datastore may have different performance characteristics (e.g., capacity, input/output operations per second or IOPS capabilities, etc.), usage of such shared local disks to store virtual disks or portions thereof may be distributed among the virtual machines based on the needs of each given virtual machine. This approach provides enterprises with cost-effective performance. For instance, distributed storage using pooled local disks is inexpensive, highly scalable, and relatively simple to manage. Because such distributed storage can use commodity disks in the cluster, enterprises do not need to invest in additional storage infrastructure.
Some distributed storage systems are object-based. For example, storage objects use multiple resource characteristics of disks in the cluster, such as IOPS (input/output operations per second) and capacity of solid state disks and magnetic disks to provide storage to clients (e.g., virtual machines). Therefore, efficient use of the disks is an important concern. One issue related to efficient disk usage is minimizing write amplification in solid state disk drives. As is known, write amplification is an undesirable phenomenon associated with SSDs where the actual amount of physical information written is a multiple of the logical amount intended to be written. Because SSD blocks must be erased before being rewritten, the process to perform these operations results in moving data and metadata more than once. Doing so creates a large amount of write overhead in disks with a high rate of I/O operations, resulting in overall slower write operations. In addition, because SSDs have a finite amount of write operations, a high amount of write amplification decreases the lifespan of a SSD.